varying float vSize;
uniform vec3 uColor;

void main(){

    float distanceToCenter = distance(gl_PointCoord, vec2(0.5, 0.5));
    // 强弱程度
    float strengh = 1.0 - (distanceToCenter * 2.0);

    if(vSize<= 0.0){
gl_FragColor = vec4(1.0, 0.0, 0.0, 0.0);
    }else {
        gl_FragColor = vec4(1.0, 0.0, 0.0, strengh);
    }
    
}